US20230278464A1 - Method for Determining the Respective Temperature of Several Battery Cells of a Vehicle Battery Via Extrapolation of a Measured Temperature; Control Device and Vehicle Battery - Google Patents

Method for Determining the Respective Temperature of Several Battery Cells of a Vehicle Battery Via Extrapolation of a Measured Temperature; Control Device and Vehicle Battery Download PDF

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US20230278464A1
US20230278464A1 US18/002,371 US202118002371A US2023278464A1 US 20230278464 A1 US20230278464 A1 US 20230278464A1 US 202118002371 A US202118002371 A US 202118002371A US 2023278464 A1 US2023278464 A1 US 2023278464A1
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Prior art keywords
resistance
measured
temperature
battery cell
battery
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English (en)
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Alexander Fill
Arber Avdyli
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Mercedes Benz Group AG
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Mercedes Benz Group AG
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01K—MEASURING TEMPERATURE; MEASURING QUANTITY OF HEAT; THERMALLY-SENSITIVE ELEMENTS NOT OTHERWISE PROVIDED FOR
    • G01K7/00—Measuring temperature based on the use of electric or magnetic elements directly sensitive to heat ; Power supply therefor, e.g. using thermoelectric elements
    • G01K7/42—Circuits effecting compensation of thermal inertia; Circuits for predicting the stationary value of a temperature
    • G01K7/427—Temperature calculation based on spatial modeling, e.g. spatial inter- or extrapolation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
    • B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
    • B60L58/24—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries for controlling the temperature of batteries
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L58/00—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles
    • B60L58/10—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries
    • B60L58/18—Methods or circuit arrangements for monitoring or controlling batteries or fuel cells, specially adapted for electric vehicles for monitoring or controlling batteries of two or more battery modules
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/48—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte
    • H01M10/486—Accumulators combined with arrangements for measuring, testing or indicating the condition of cells, e.g. the level or density of the electrolyte for measuring temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/40—Drive Train control parameters
    • B60L2240/54—Drive Train control parameters related to batteries
    • B60L2240/545—Temperature
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B60—VEHICLES IN GENERAL
    • B60L—PROPULSION OF ELECTRICALLY-PROPELLED VEHICLES; SUPPLYING ELECTRIC POWER FOR AUXILIARY EQUIPMENT OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRODYNAMIC BRAKE SYSTEMS FOR VEHICLES IN GENERAL; MAGNETIC SUSPENSION OR LEVITATION FOR VEHICLES; MONITORING OPERATING VARIABLES OF ELECTRICALLY-PROPELLED VEHICLES; ELECTRIC SAFETY DEVICES FOR ELECTRICALLY-PROPELLED VEHICLES
    • B60L2240/00—Control parameters of input or output; Target parameters
    • B60L2240/40—Drive Train control parameters
    • B60L2240/54—Drive Train control parameters related to batteries
    • B60L2240/547—Voltage
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/42—Methods or arrangements for servicing or maintenance of secondary cells or secondary half-cells
    • H01M10/425—Structural combination with electronic components, e.g. electronic circuits integrated to the outside of the casing
    • H01M2010/4278—Systems for data transfer from batteries, e.g. transfer of battery parameters to a controller, data transferred between battery controller and main controller
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M2220/00—Batteries for particular applications
    • H01M2220/20—Batteries in motive systems, e.g. vehicle, ship, plane
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/10—Energy storage using batteries
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02T—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION
    • Y02T10/00—Road transport of goods or passengers
    • Y02T10/60—Other road transportation technologies with climate change mitigation effect
    • Y02T10/70—Energy storage systems for electromobility, e.g. batteries

Definitions

  • the invention relates to a method for determining the respective temperature of several battery cells of a vehicle battery.
  • a second aspect of the invention relates to a corresponding control device.
  • a third aspect of the invention relates to a vehicle battery having the stated control device, among others.
  • Electric motor vehicles must be able to fulfil the high expectations and requirements that are already fulfilled by conventional fuel-powered vehicles with regards to lifespan, performance, range and safety for a successful commercialisation.
  • Purely electric vehicles that only have an electrical energy storage and one or several electric motors, hybrid vehicles that have a combustion engine, an electrical energy storage and one or several electric motors, and hydrogen vehicles that, for example, have a fuel cell, an electrical energy storage and one or several electric motors, are examples of electric motor vehicles.
  • An electrical energy storage of a motor vehicle can also be described as a vehicle battery and/or traction battery.
  • a vehicle battery is composed of a plurality of battery cells that are interconnected among each other in series and/or in parallel. The plurality of battery cells is designed to save electrical energy collectively, or to collectively provide an electrical power.
  • the battery cells of a vehicle battery can all be interconnected in series. It is advantageously provided, however, that several battery cells are interconnected with each other in series, and yield a group wherein several such groups are interconnected in parallel.
  • the nominal voltage level of the vehicle battery results from the nominal voltage of the individual battery cells and the number of battery cells interconnected in series.
  • the nominal voltage level is preferably at least 80 volts, preferably at least 200 volts, for example 400 volts or 800 volts.
  • the vehicle battery is continuously monitored in order to guarantee an efficient and safe operation of the vehicle battery or of the motor vehicle having the vehicle battery.
  • the respective temperature, voltage, current, state of charge (SoC) and/or the degree of wear or degradation (state of health, SoH) is checked, for example. Any combination of the variables given as examples is here possible. It is extremely advantageous to continuously check, or to determine and to monitor the respective temperature of each of the battery cells in an operation. This applies analogously to the degree of wear or the degradation (SoH).
  • the arrangement of a respective temperature sensor on each battery cell is here extremely complicated and cost intensive. Correlations between the given variables and the internal resistance of the respective battery cells are frequently utilised for this reason. The temperature and/or the degradation of the respective battery cell can in particular be determined from the internal resistance.
  • the internal resistance of a respective battery cell can for example be used by means of a current pulse measuring method that utilises a correlation of a voltage response to a current pulse.
  • a low computational effort is necessary for this purpose. Values determined in this way can only be provided irregularly, however.
  • An alternative method uses an adaptive model, for example a so-called electric circuit model (ECM). This relates in particular to a Kalman filter.
  • ECM electric circuit model
  • a first aspect of the invention relates to the method for determining the respective temperature of several battery cells of a vehicle battery.
  • the method has the following steps:
  • the determination of the measured values occurs in particular via a corresponding measurement by means of a measurement device.
  • the measurement device can in particular be designed to measure the first voltage and/or the second voltage and/or the respective current.
  • the respective current that flows through the first battery cell and the second battery cell is in particular the same current, as both battery cells are interconnected in series.
  • the first measured resistance and the second measured resistance can be determined by means of the measured values.
  • the determination of the first and second measured resistance occurs in particular by means of a mathematical correlation between current voltage and resistance.
  • the determination of the first measured resistance of the first battery cell and the second measured resistance of the second battery cell from the measured values occurs by means of Ohm’s law, for example. More complicated mathematical correlations can also be used in a further embodiment, as will further be shown in the further course of this application.
  • the reference resistance can be a predetermined value, for example.
  • the determination of the reference resistance can occur in this case by requesting the predetermined value from a storage device.
  • the reference resistance can alternatively be formed as an average value of all measured resistances of the several battery cells, for example the first measured resistance and the second measured resistance.
  • the determination of the reference resistance occurs in particular by means of averaging or forming the average of all measured resistances of all battery cells of the vehicle battery.
  • the first and the second measured resistance relationship can be formed by dividing the respective measured resistance, and thus the first or the second measured resistance, by the reference resistance.
  • the first or second reference resistance can alternatively be formed by distributing the reference resistance by the first or the second reference resistance.
  • the determination of the measured temperature of the first battery cell can occur by measuring the temperature of the first battery cell.
  • the determination or measurement of the measured temperature in particular occurs by means of a temperature sensor.
  • the temperature sensor can for example be formed as an NTC or PTC sensor, or comprise a sensor of this kind.
  • a measurement by means of an infrared thermometer is alternatively also possible. Any other measuring method for measuring a temperature of the first battery cell is also conceivable.
  • the measured temperature of the first battery cell can generally be determined by means of a temperature measuring unit.
  • the determination of the computed temperature occurs on the basis of the first resistance relationship und the second resistance relationship, and the measured temperature according to the predetermined requirement.
  • the computed temperature here indicates the temperature of the second battery cell, while the measured temperature indicates the measured temperature of the first battery cell.
  • the computed temperature is described as such as it is not measured, but is rather derived or determined from the given variables by means of the predetermined requirement.
  • the invention is based on the idea of extrapolating the temperature of the second battery cell from the temperature of the first battery cell.
  • the measured temperature is compared with the first and the second resistance relationship for this extrapolation.
  • the invention here takes advantage of the fact that the internal resistance of a respective battery cell decreases when the temperature of the corresponding battery cell increases.
  • the temperature of the first battery cell can thus be extrapolated to the second battery cell based on the respective internal resistance, and thus on the first and second measured resistance of the first and second battery cell.
  • there is no linear relationship between the temperature and the respective internal resistance can be available via a distribution function and/or a corresponding value table, for example.
  • the relationship, in particular the distribution function or the value table can here be predetermined.
  • the relationship, in particular the distribution function or the value table is in particular derived via corresponding tests on a vehicle battery of this kind or corresponding battery cells.
  • a numerical generation of the value table or the distribution function can here be provided.
  • the method is generally also possible without the steps of determining the reference resistance and determining the first and second resistance relationship.
  • the computed temperature could occur differently by means of the measured temperature, and the first measured resistance and the second measured resistance according to a corresponding predetermined requirement.
  • the comparison with the reference resistance also described as normalization, can deliver reliable results.
  • This here proceeds from the knowledge that the absolute resistances are not of interest, as the respective battery cell having the lowest internal resistance is usually also the warmest of the battery cells, and the battery cell having the highest internal resistance is usually the coolest of the battery cells.
  • the determination of the computed temperature also occurs independently of the measured temperature, the observation of the respective measured resistance normalized to the reference resistance, and thus to the first or second resistance relationship, is sufficient.
  • a homogeneous database is obtained via normalization.
  • the predetermined requirement contains the distribution function and/or the value table that assign a respective value, in particular exactly one respective value, for the temperature, and thus the computed temperature, to a plurality of values for the second resistance relationship, depending on the measured temperature and the first resistance relationship.
  • the distribution function and/or the value table are generated via the corresponding tests or measurements on the vehicle battery.
  • the value table or the distribution function can be provided via a mathematical relationship or a mathematical formula, or numerically.
  • the value table and/or the distribution function can additionally have the discharge state of the vehicle battery and/or the respective battery cell as parameters.
  • the respective relevant distribution function and/or value table can be consulted for different values of the state of charge of the vehicle battery and/or the respective battery cell.
  • the method can contain the determination of a state of charge of the vehicle battery and/or the respective battery cell as an additional step. An even more precise determination of the temperature, in particular computed temperature of the second battery cell, can be obtained in this way.
  • the distribution function and/or value table is first normalized depending on the first resistance relationship and the measured temperature, and the computed temperature is then derived from the normalized distribution function and/or value table depending on the second resistance relationship.
  • the distribution function and/or value table is selected or generated by means of the data of the first battery cell, and thus the first resistance relationship and the measured temperature, and then the computed temperature is selected from the distribution function and/or value table generated in this way, depending on the second resistance relationship.
  • the normalized distribution function and/or value table can here indicate a one-to-one relationship between computed temperature and second resistance relationship. In this way, it is possible to easily derive the computed temperature by means of the normalized distribution function and/or value table.
  • the normalization or generation or selection of the normalized distribution function and/or value table can occur in particular on the basis of predetermined data.
  • a respective second resistance relationship for several second battery cells is determined, from which, and by means of the predetermined requirement, the measured temperature and the first resistance relationship, a respective value for the computed temperature of the respective second battery cell is determined.
  • the determination of the computed temperature of the second battery cell occurs in an analogue manner for several second battery cells in parallel.
  • the respective second resistance relationship can here be used as the basis for each of the second battery cells, the second resistance relationship being derived from a respective measured resistance that is determined for the respective second battery cell.
  • a respective second voltage can be determined for each of the second battery cells to determine the respective second measured resistance.
  • a respective current can be determined for each of the second battery cells, wherein the respective current can be the same for all second battery cells in the event of an interconnection in series.
  • the respective computed temperature of the respective second battery cell is here determined in each case on the basis of the first resistance relationship of the first battery cell and the measured temperature of the first battery cell.
  • the computed temperature of each of the second battery cells is extrapolated on the basis of the measured temperature of the first battery cell and its resistance or resistance relationship. In this way, a plurality of temperature sensors is not required, as a temperature sensor is no longer needed for each of the second battery cells.
  • a respective measured temperature and a respective first resistance relationship is determined for several first battery cells, from which, and by means of the predetermined requirement and the second resistance relationship, a respective value for the computed temperature of the second battery cell is determined.
  • the computed temperature of the second battery cell is extrapolated on the basis of the respective measured temperature and the respective first resistance relationship of several first battery cells.
  • the determination or extrapolation of the computed temperature occurs in particular on the basis of the different battery cells independently of each other.
  • the several values for the computed temperature of the second battery cell are averaged.
  • Outliers and thus values for the computed temperature of the second battery cell that deviate from the usual values by more than a predetermined amount, can be filtered out before this averaging occurs. This is because values deviating significantly in this way or outliers are probably due to errors in the measuring or errors in the determination of the computed temperature. In this way, the precision in the determination of the respective temperature of the battery cells can be further improved.
  • At least one measured temperature of one of the several first battery cells arranged on the edge of the vehicle battery and at least one measured temperature of one of the several first battery cells arranged in the center of the vehicle battery is determined.
  • a respective temperature sensor or a respective temperature measuring unit is arranged on at least one first battery cell that is arranged on the edge of the vehicle battery, and at least one temperature sensor or temperature measuring unit is arranged on a first battery cell that is arranged in the middle of the vehicle battery.
  • the first battery cell arranged on the edge of the vehicle battery is only next to one further battery cell, for example.
  • the first battery cell arranged in the middle of the vehicle battery is next to a respective further battery cell on several sides, for example.
  • a correlation coefficient G is greater than a predetermined value and/or respective measured temperatures of several first battery cells among themselves do not exceed a predetermined measurement in the reference state.
  • the correlation coefficient G applies in particular to the quality of a regression of the determination of the respective measured resistances.
  • the correlation coefficient G here represents in particular a quality factor that characterises the data quality of the measured values or resistance values derived from them.
  • the reference state is here in particular a static state in which the vehicle battery is in a static state. The determination of the respective temperature of the several battery cells is not required in the reference state, or exactly when the reference state is present, as it can be assumed that these develop in a temporally constant manner.
  • a second aspect of the invention relates to a control device for determining the respective temperature of several battery cells of a vehicle battery, wherein the control device is designed to:
  • the control device is in particular designed to carry out the method according to the invention according to one or several of the embodiments described here.
  • the control device comprises a computing unit, for example, the computing unit being formed as a microcontroller, field programmable gate array (FPGA) or digital signal processor (DSP).
  • the control device or the computing unit can have a memory unit, for example a flash memory, a magnetic memory medium, and/or an optical memory medium or the like, in which a computer program product is saved that contains program coding means to carry out the method according to the invention or individual method steps of the method according to the invention.
  • the program coding means in particular provide for the execution of the method according to the invention according to one or several embodiments when executed on the control device or the computing device.
  • a third aspect of the invention relates to the vehicle battery having:
  • the vehicle battery can be executed as a lithium-ion battery, for example.
  • the vehicle battery can have a voltage level of more than 80 volts, preferably more than 200 volts, for example 400 volts or 800 volts.
  • the vehicle battery in particular has several temperature measuring units, for example two, three or four. In this case, four battery cells of the vehicle battery are first battery cells in the sense of the present application.
  • the respective temperature of the remaining battery cells of the vehicle battery, the battery cells also being able to be described as second battery cells in the sense of the present application, is extrapolated by means of the respective measured temperatures of the first battery cells or the one first battery cell.
  • FIG. 1 shows a schematic block diagram of a vehicle battery having several battery cells, wherein some of the battery cells have a respective temperature sensor, and the temperature of the remaining battery cells is extrapolated by means of the measured temperatures and respective resistances of the battery cells;
  • FIG. 2 shows an exemplary method sequence with reference to a process diagram
  • FIG. 3 shows an exemplary experimentally provided distribution function.
  • FIG. 1 shows a vehicle battery 1 having a plurality of battery cells 2 according to an extremely exemplary embodiment.
  • the battery cells 2 are divided into two groups 3 , wherein the battery cells 2 of a respective group 3 are respectively interconnected in series.
  • the groups 3 are interconnected with each other in parallel in turn. Every other reasonable interconnection of the battery cells 2 is of course also possible.
  • the vehicle battery 1 is in particular formed as a so-called traction battery to provide an electric drive of a motor vehicle having electrical energy to drive or accelerate a motor vehicle.
  • the vehicle battery 1 or its battery cells 2 are in particular based on the technology of a lithium-ion battery.
  • the vehicle battery 1 has electrical ports 5 to which an output voltage of the vehicle battery 1 is applied.
  • a load in particular an inverter for operating an electric machine of a motor vehicle and/or a voltage transformer for providing an on-board power supply of the motor vehicle with electrical energy can in particular be applied to the electrical ports 5 .
  • the vehicle battery 1 can emit electrical energy or an electrical power outwards via the electrical ports 5 .
  • the electrical ports 5 for providing the electrical power can be the only power requirements that are led out of a battery housing 6 of the vehicle battery 1 .
  • the electrical ports 5 can be provided by two poles in total.
  • the output voltage of the vehicle battery 1 is nominally in particular more than 80 V, preferably more than 200 V, for example 400 V or 800 V.
  • the number of battery cells 2 interconnected in series also derives from the desired nominal voltage level of the output voltage when lithium-ion based battery cells 2 are used.
  • a monitoring of the vehicle battery 1 that is as comprehensive as possible is necessary in order to be able to guarantee a high degree of safety during the operation of the vehicle battery 1 and to maximise a lifespan of the vehicle battery 1 .
  • the monitoring can for example relate to the output voltage, a current flow, a temperature, a state of charge (SOC), a degradation (SOH) or the like. It is particularly preferred if this monitoring occurs not only in relation to the entire vehicle battery 1 , but at least partially for each of the battery cells 2 individually. In this way, damage to individual battery cells 2 can be recognised or prevented.
  • the vehicle battery 1 has several temperature measuring units 4 .
  • the temperature measuring units 4 are assigned to a respective battery cell 2 .
  • the temperature measuring units 4 are here designed to measure the temperature of the respective battery cells 2 .
  • the battery cells 2 to which a temperature measuring unit 4 is assigned are also described as first battery cells 11 . It is obvious that a temperature measuring unit 4 is only assigned to a fraction of the battery cells 2 .
  • the battery cells 2 to which no temperature measuring unit 4 is assigned are also described as second battery cells 12 . Only a few temperature measuring units 4 are provided, in order to keep a complexity and production costs of a vehicle battery 1 as low as possible.
  • it is desirable to determine the respective temperature of all the battery cells 2 it is desirable to determine the respective temperature of all the battery cells 2 . For this reason, the measured temperature of the first battery cells 11 is extrapolated to the second battery cells via a method for determining the respective temperature of battery cells of the vehicle battery 1 .
  • the vehicle battery 1 can have a corresponding control device 9 to carry out this method.
  • the vehicle battery 1 presently has a measuring device 7 that is designed to measure or determine current and voltage of the individual battery cells 2 .
  • a respective voltage for each of the battery cells 2 is measured or determined.
  • the current for each of the battery cells 2 is measured independently of each other.
  • the current is preferably measured or determined for several battery cells 2 together, however.
  • the respective current that flows through the battery cells 2 interconnected in series, presently the battery cells 2 of a group 3 is respectively the same due to the series interconnection of several battery cells 2 . In this way, the current can respectively only be measured once for each of the groups 3 .
  • the entire current of all the groups 3 can alternatively be measured and distributed over the number of the groups 3 , this occurs in particular under the assumption that the entire current is equally distributed over all the groups 3 .
  • the current of a group 3 can be measured and it can be assumed that the current of the other groups 3 corresponds to this current.
  • the measurement of the given measured value corresponds to a step S 1 in relation to the process diagram according to FIG. 2 .
  • the measured values are alternatively or additionally received via the control device 9 in the step S 1 .
  • a respective resistance also a measured resistance
  • This determination of the respective resistances or internal resistances of the individual battery cells 2 corresponds to a step S 2 .
  • a reference state or a so-called “steady state” is present.
  • the respective temperature of the first battery cells 11 differs from one another at most by a predetermined amount in the present embodiment in this reference state.
  • a correlation coefficient G is also greater than a predetermined value in the present embodiment in the reference state.
  • the correlation coefficient G is described in more detail in the following (see also formula (22)). If a reference state of this kind is present, the method for determining the respective temperature is halted or carried out in a different manner. In this case, the temperature of the second battery cells 12 is not determined, this corresponds to the path “n” in the process diagram, but rather the degradation (“state of health”) of the battery is determined, which corresponds to the path “y” in FIG. 2 .
  • step S 6 the temperature values are requested or received from the temperature measuring units 4 . This occurs in particular via the control device 9 .
  • the measurement of the temperature values can also alternatively or additionally occur in the step S 6 via the temperature measuring units 4 .
  • the step S 6 can be carried out repeatedly and/or be carried out before the step S 3 , such that the temperature values for the step S 3 are respectively provided in current form.
  • a reference resistance is determined.
  • This reference resistance can for example be a predetermined value that is requested during the step S 4 from a memory unit of the control device 9 .
  • the reference resistance is determined from the internal resistances or measured resistances of all the battery cells 2 .
  • the reference resistance is in particular determined via averaging of the same. In other words, the reference resistance can be the average of the internal resistances or measured resistances.
  • a respective resistance relationship is determined for each of the internal resistances of the battery cells 2 in the step S 5 .
  • This respective resistance relationship is calculated by dividing the respective internal resistance or measured resistance by the reference resistance.
  • the respective resistance relationship can alternatively be calculated by dividing the reference resistance by the respective internal resistance or measured resistance.
  • a respective computed temperature of all the second battery cells 12 is here determined on the basis of the measured temperatures via the respective resistance relationships.
  • the basis of the computed temperature can here be a predetermined requirement.
  • the predetermined requirement in particular connects the respective temperatures of the battery cells 2 to the respective resistance relationship.
  • the predetermined requirement can here contain a value table and/or a distribution function 15 .
  • the value table and/or distribution function 15 can be derived in particular from corresponding laboratory tests. The results of the corresponding laboratory tests can be numerically contained in the value table and/or distribution function, or can be emulated via a mathematical function.
  • FIG. 3 shows an exemplary distribution function 15 that specifies the temperature T R of a respective second battery cell 12 , depending on the respective resistance relationship V R2 of the corresponding second battery cells 12 and the state of charge SOC.
  • the exemplary distribution function 15 is here generated as a parameter on the basis of the first resistance relationship and the measured temperature of a respective first battery cell 11 .
  • a distribution function 15 based on the measured temperature and a first resistance relationship of a respective first battery cell 11 is generated, in order to derive the temperature T R of a respective second battery cell 12 from the distribution function, depending on its resistance relationship V R2 and state of charge SOC. In a further embodiment, this can occur for each second battery cell 12 independently of each other on the basis of each first battery cell 11 .
  • the basis for the determination or calculation of the respective internal resistance is a sub-division of the course of the measured variables (current and voltage) into an instant system response I(t)•R Ohm (t) and a delayed system response F(t).
  • the instant system response is described via the voltage on the ohmic resistance R Ohm (t) due to the current I(t).
  • the delayed system response F(t) is in turn sub- divided into a deterministic ratio F deter and a stochastic noise ratio Fstoch
  • the delayed deterministic cell behaviour can be expressed by using an electric circuit model (ECM) having two resistance pairs.
  • ECM electric circuit model
  • the stochastic noise can be expressed via an independent Gaussian noise method having a mean average value of zero.
  • the values of the ECM parameters R Ohm , R Pol , R Diff , C Pol , C Diff and C N change over time depending on operating conditions and cell states.
  • the requirements of the usage of stochastic methods require the voltage and current signals to be discretised into sample values.
  • the discrete signals are combined into a vector
  • One possible way of determining the ohmic resistance is therefore to apply the covariance of the voltage vector to the current vector
  • equation 19 can be approximated by means of the equations (9) - (15):
  • This application comprises two different techniques of the regression method.
  • One method requires a data backup of the respective sample in order to analytically calculate the covariance and the correlation coefficient.
  • the other algorithm approximates the covariance and the correlation coefficient while avoiding the need for an interim storage.
  • the two algorithms are completely described in the following, including filters used, starting values and definitions.
  • R I , k Cov ⁇ I ⁇ k , ⁇ U ⁇ k V ⁇ I ⁇ k
  • R I , k R I , k , if V ⁇ I ⁇ k ⁇ 0 ⁇ R I , k ⁇ R + ⁇ R I , k ⁇ ⁇ R I , k ⁇ 1 , else
  • R I , k ⁇ 1 ⁇ ⁇ ⁇ R I , k ⁇ 1 ⁇ + ⁇ ⁇ R I , k
  • ⁇ ⁇ k + 1 1 ⁇ ⁇ ⁇ ⁇ ⁇ k + ⁇ ⁇ ⁇ d ⁇ k + 1 ,
  • R I , k C k 1 , 2 C k 1 , 1
  • R I , k R I , k , if C k 1 , 1 ⁇ 0 ⁇ R I , k ⁇ R + ⁇ R I , k ⁇ ⁇ R I , k ⁇ 1 , else
  • R I , k ⁇ 1 ⁇ ⁇ ⁇ R I , k ⁇ 1 ⁇ + ⁇ ⁇ R I , k
  • ⁇ ⁇ k + 1 1 ⁇ ⁇ ⁇ ⁇ ⁇ k + ⁇ ⁇ ⁇ d ⁇ k + 1 .
  • the output of the described data-based algorithms leads to a resistance distribution R I,k of the lithium-ion cells within the vehicle battery 1 .
  • This distribution is comprised of degradation (SoH) and temperature gradients, and tolerances in cell production and module design.
  • SoH degradation
  • temperature gradients tolerances in cell production and module design.
  • R R ⁇ N ⁇ j . / N R x i , j ⁇ ­­­(24)

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